Processing well fluids



July-13, 1943. G. L. PARKHURST 2,324,172

PROCESSING WELL FLUIDS Filed oct. s1, 1940 s sheets-sheet 1 5Sheets-Sheet 2 G. l.. PARKHURST PROCESSING WELL FLUIDS Filed oct. :51,1940 July 13, 1943.

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July 13, 1943. G. L.. PARKHURST 2,324,172

PROCESSING WELL FLUIDS Filed 0012. 5l, 1940 3 Sheets-Sheet 5 PatentedJuly 13, 1943 PnocnssrNG WELL FLUms George L. Parkhurst, Chicago, Ill.,assignor to Standard Cil Company, Chicago, Ill., a corporation ofIndiana j Application october 31, 1940, serial No. 363,737

3 Claims. (Cl. lii-50) This invention relates to methods of hydrocarbonconversion and recycle which are particularly applicable for useinconnection with wells of the so-called distillate or condensate type.The method is applicable also in connection with production from othertypes of wells when it is desired to cycle gas to repressure anunderground formation. More particularly this invention relates to acombination of distillate recovery and the Fischer or Fischer-Tropschprocess.

Production from certain deep hydrocarbon reservoirs of the so'-cal1eddistillate type is wholly or largely in the vapor phase although thesevapors contain substantial amounts of normally liquid hydrocarbonscommonly including gasoline hydrocarbons and hydrocarbons boilingsomewhat above the gasoline range. The existence of these hydrocarbonsin the vapor phase in the subsurface reservoir is due to the highpressure existing in the formation which brings into play the so-calledretrograde phenomena, whereby a hydrocarbon system which would exist asa liquid phase plus a vapor phase at moderate pressures exists as asingle dense vapor or supercritical phase.

If gases coming from these extremely high pressure wells, e. g. atpressures of the order of 2000'to 4000 pounds per square inch, arereduced in pressure to pressures of the order of 700 to 1200 pounds persquare inch, a distillate or condensate is formed. In handling' theproduction from such reservoirs the well uids are reduced in pressureand sometimes cooled to bring about the phenomenon of retrogradecondensation, whereby a large part of the normally liquid hydrocarbonsand also a substantial part of three and four carbon atom hydrocarbonsare thrown out in the liquid phase and separated. This liquid phase canthen be stabilized or flashed to atmospheric pressure. The gasesoriginally separated, and sometimes those resulting 'from thestabilization or flashing operation are recycled to the undergroundformation from which they were pro. duced, thereby maintaining thepressure in such formation and preventing retrograde condensationtherein, thus greatly improving the ultimate recovery from thereservoir. In some instances, these gases are used for the maintenanceof the pressure in or the repressuring of an underground formation'other than that from which they originated. ,e

It has been proposed to recover the liquid components of high pressurewell fluids of the type described by a high pressure absorption or highpressure adsorption process followed by recycling of the gases to thesame or another sub-surface reservoir for pressure maintenance orrepressuring purposes.

Although the present invention is particularly applicable to productionfrom high pressure weils of the distillate type, it is also applicableto ordinary gas wells, particularly where natural gasoline is present inthe gas and to wells producing a liquid phase as well as a gas phase atthe well head.

It is an object of my invention to increase the quantity of motor fuelproduced from well uids of the distillate type. Further, it is an objectof f this invention to provide repressuring gases having an increasedability to promote retrograde vaporization or prevent retrogradecondensation in the reservoir. It is also an object to provide a processin which increased quantities of motor fuel are obtained from wellliuids of the distillate type and in which the quantity and quality ofthe repressuring gases are increased. A more particular object is toprovide a process in which at least a part of the gases remaining aftera distillate recovery operation are so treated as to produce a syntheticcrude oil which can be further processed to motor fuel. Other objectswill appear hereinafter.

The production from distillate wells normally includes a large amount ofmethane and lesser amounts of higher paralnic hydrocarbons. Ordinarilythis includes a substantial amount of Cz, C3 and C4 hydrocarbons, withasubstantial amount of hydrocarbons within the gasoline boiling range, i.e. up to about 400 F., and usually some still heavier hydrocarbons invarying amounts. In distillate recovery, whether by retrogradecondensation vor high pressure absorption, it is customary to recyclepractically all of the C1, Cz andv C3 hydrocarbons and often a largepart of the C4 hydrocarbons to the underground formation. The desirablenormally liquid hydrocarbons are recovered and are not available for Theabove and other objects are accomplished by subjecting to catalyticoxidation certain of the light hydrocarbons present in the dry gasresulting from a distillate recovery operation to produce a synthesisgas comprising carbon monoxide and hydrogen. This synthesis gas issubjected to a Fischer or Fischer-Tropsch process,v and high pressurenitrogen and/or hydrogen is cycled to the input well.

Briefly, this method is followed by ilrst separating the distillate fromgases by retrograde condensation or by high pressure absorption atpressures of about 1000 pounds per square inch or more. These gases areprocessed as outlined below. The distillate is separated into apredominantly Cs and C4 fraction, a light naphtha in the gasolineboiling range and a heavy naphtha. 'I'he normally gaseous Ca and C4hydrocarbons may be subjected at high temperatures and preferably athigh pressures to a thermal polymerization Aprocess which produces notonly a large amount of gasoline range hydrocarbons but also an amount ofgas of even greater volume than the gaseous volume of the hydrocarbonsgoing to the polymerization operation. I'hese gases are available forrecycling. The thermal polymerization process involves, among otherreactions, the dehydrogenation oi' Ca and C4 hydrocarbons and of ethaneto some extent, and the polymerization of the olefinic hydrocarbons thusproduced to form normally liquid hydrocarbons ordinarily boiling largelyin the gasoline range but including a heavy polymer fraction, which isvery useful in connection with a high pressure absorption operation. Theoverhead from the initial Fischer product separation comprising mainlyC3 and C4 olefins can be subjected to catalytic polymerization and thepolymer combined with the product from the distillate C3-C4 thermalpolymerizer. This combined stream is further fractionated and cycled asdescribed in detail in connection with the drawings.

In a preferred process the normally gaseous hydrocarbons remaining afterrecovery of -the liquid hydrocarbons from the high pressure well fluidsand comprising predominantly methanev are desulfurized and subjected tocracking in the presence of oxygen to produce a synthesis gas comprisingcarbon monoxide and hydrogen.

The methane or gas fraction can be cracked to produce the synthesis gasmixture consisting largely of carbon monoxide and hydrogen by any of avariety of processes. Thus it can be reacted with steam or with oxygen.Preferably the dry gas is cracked in the presence of oxygen producedeither by electrolysis of water or by a low temperature distillationprocess from air. For example, the oxygen necessary for thisgas-cracking step canbe produced by the Linde or Linde- Frnkl process.This results in a volume of high pressure nitrogen which theoreticallywill be equal to twice the volume of 'methane cracked, since one-halfmol of oxygen will theoretically be usedy for each mol of methane andabout two mols of nitrogen will be produced for each half mol of oxygen.This nitrogen is available at an elevated pressure and can be useddirectly' for reinto an underground reservoir to increase or maintainits pressure and displace the hydrocarbons in that reservoir towards theoutlet wel! or wells. Thus electrolysis yields hydrogen and the oxygenconcentration yields nitrogen under high pressure. v

Alternatively or additionally the tail gases from the Fischer orFischer-,Tropisch process can be compressed and recycled through theformation or sent to another formation to displace the hy-4 drocarbonfluids en masse towards the output well or wells and to prevent theprecipitation of liquids within the reservoir which would result from apressure drop. These tail gases not only contain hydrogen as theprincipal component but also contain nitrogen, carbon monoxide and lighthydrocarbons and enhance the operation of the retrograde phenomena.

Ii the gas cracking is carried out with steam rather than oxygen, anexcess of hydrogen will exist in the synthesis gas and in the tail gasfrom the Fischer process. 'Ihese tail gases particularly high inhydrogen are highly beneficial for cycling to a sub-mirface reservoir toincrease or maintain the pressure in the reservoir thus increasing theultimate recovery of valuable hydrocarbons from the reservoir.

The normally gaseous hydrocarbons heavier than methane, i. e. Cz and/orC: and/or C4 hydrocarbons, can be separated wholly or in part in one ormore fractions from the products of the Fischer synthesis oven, whichcan be operated in one or two or more stages with or without anintermediate product recovery step. All or part of the normally gaseousproducts can be recycled to the gas-cracking step or can be compressedand cycled to the input well. Likewise, someof the gaseous hydrocarbonsfrom the Fischer process can be cycled to fuel. It will be apparent tothose skilled in the art that the ultimate disposition of the gasesremaining after the various separations will vary depending not onlyupon the composition of the well fluid undergoing recovery but also uponthe manner in which the various steps are operated. Various economicconsiderations will enter to determine further what is to be done withthe various gas fractions otherthan the methane fraction from thedistillate recovery. Ordinarily the methane fraction iscracked tosynthesis gas and the hydrogen, nitrogen and 'Fischer tail gasesordinarily are sent to an underground formation under pressure, thehydrogen and nitrogen being under considerable pressure.

In a preferred process,` the gases comprising the methane fractionremaining after recovery of liquid hydrocarbons from the well fluids arecracked to produce a synthesisgas mixture made up largely of carbonmonoxide and hydrogen. Any of a variety of processes can be used, forexample, the gases can be reacted with steam or with oxygen. Somehydrocarbons oi' higherA molecular weight thanmethane canbefincluded inthe methane fraction separated vfr Qm the well fluid,l particularlywhere their presence fserves to produce a better balancedvsynthesis,gasmixf` ture and the synthesis gas can,v.if desired-bc madeentirely from C2 and Cs. Q1f`Cz, Cs.,and,C4'-

bons heavier thanmethane, i. e., the C: and/or Ca and/or C4hydrocarbons, can be separated wholly or in part in one or morefractions from the liquid products of the Fischer synthesis. Therecovered gases can be recycled in whole or in part to the sas-crackingstep or the synthesis gas step or they can be thermally or catalyticallypolymerized. An intermediate fraction of the Fischer synthesis productcan be thermally or catalytically polymerized to liquid hydrocarbonseither separately or along with the distillate hydrocarbons. Hydrogenproduced by either the thermal or catalytic treatment o; thehydrocarbons can, of course, be forced down a well to repressure anunderground formation. y

In order that the invention may be better understood, reference is madeto the accompanying drawings which show in Figures 1, 2 and 3 flowdiagrams illustrating my invention and forming a part of thisspecification. 4 Referring first to Figure l, a producing well I0furnishes well iluids from a sub-surface reservoir which is normally adeep high pressure well of the distillate type. The well fluids passthrough valve II and line I2 to one or the other of drlers 28. Thesedriers may contain any desired drying material, for example, calciumchloride. The particular drier used at any particular time is controlledby the operation of valves 00. Normally one drier is onstreaxn and theother is being regenerated by passing hot gases therethrough by means ofvalves 21. The purpose of the drying operation is to remove water whichwould otherwise form natural gas hydrates on reduction of thetemperature and pressure, thereby interfering with the operation of thesubsequent apparatus. and pressure of the separation step are such thathydrate formation is not objectionable. the drying step can be omitted.

'I'he well iiuids pass through cooler I3 and pressure reduction valve I4to separator I5. The cooler and pressure reduction valve are controlledto give a temperature and pressure in the separator I 5 which may bevaried within considerable limits depending on the desired operation andthe particular character of the well fluids. However, they are such asto give a substantial recov- However, if the temperature ery of liquidhydrocarbons by virtue of the retrograde condensation phenomenon.

'I'he gas phase from separator I5 is predominantly methane but alsoincludes ethane and minor amounts of heavier hydrocarbons. 'I'his gasvphase passes through line I8 -to methane cracker or synthesis gasgenerator |40, where it undergoes an exothermic catalytic oxidation. (If

necessary the gasesfrom separator |5 may be reduced in pressure prior tointroduction to the methane cracker |40.) The liquid phase formed inseparator I5 and withdrawn through line 23 by valve 22 controlled byfloat 2|, includes a major part of normally'liquid hydrocarbons presentin the well fluids and normally gaseous hydrocarbons, particularly C3and C4 paraillnic hydrocarbons. 'I'hese gases may be recovered by knownmeans and the fraction in the gasoline boiling range passed from s'urgedrum 23 by line |13 to Fischer Process gasoline stora'ge tank 83.

The synthesis gas generator |40 is supplied with oxygen produced byelectrolysis of water with by-product hydrogen under high pressure, forexample, about 4000 pounds per square inch, or by the Linde-Frnklprocess with nitrogen under high pressure as a by-product. The hydrogenor nitrogen is cycled via line |5| to input well |52 and oxygen passesto methane cracker |40 by line |42. The synthesis gas comprising largelyhydrogen and carbon monoxide is withdrawn from methane cracker |40 byline |55 and Introduced in synthesis over IAQ. .In oven |48 the carbonmonoxide and hydrogen are reacted to produce higher molecular weighthydrocarbons largely of the gasoline boiling range. This step is wellknown in the art and it is contemplated that it may be carried out underany one of the variety of conditions under which it is known to operate.Thus it may be carried out at pressures ranging from about atmosphericup to about 150 pounds per square inch or somewhat higher, and withinthe temperature range of between above 300 F. and 400 F., althoughsomewhat higher and somewhat lower temperatures may be selected.

The synthesis product containing substantial amounts of oleflns isremoved from oven |48 by line |56 to separator |51. If desired, cooleror waste heat boiler |58 may be placed on line |58 between synthesisoven |48 and separator |51 to cool reaction products prior tointroductionto the separator |51.

Considerable quantities of water are produced in the hydrocarbonsynthesis from carbon monoxide and hydrogen and this water ordinarily isremoved from the hydrocarbons and discarded from the system by valvedline 202 in response to float control |59. When the process is operatedto produce a predominantly synthesis gasoline, it is drawn off by valvedline |62 and passed to stabilizer 32, the bottoms from stabilizer 32being drawn ofi' byline 59 through cooler 6I and thence to product tank83.

The gas phase from separator |51 is pumped to absorber |11. can be sentto fuel via valved line 206 and valve 2|0. The gases removed fromabsorber |11 viav line |81 may be recycled to the input well or may beused as fuel. The liquid product from absorber |11 is withdrawn asbottoms by valved line |18, passed in heat-exchange relation with anabsorber oil flowing in line |86 by means of heat exchanger |19 andintroduced to fractionator |80. Fractionator |80 is provided withconventional dephlegmating means |8| and with reboiler |82. The bottomsfrom fractionator |80 is pumped via valved line |83 by pump |84 throughheat exchanger |19 and cooler |85 and introduced as lean absorber oilinabsorber |11 by line |86. The gases fro'm absorber |11 comprisingpredominantly hydrogen are withdrawn by line |81 and may be compressedand recycled to the input well via. line |00. Alternatively, the gasescan be sent to fuel by valved line |9|, or they may be recycled to themethane cracker or synthesis gas generator |40.

Returning to the fractionator |80, the gas phase Withdrawn overhead byline |92 may be introduced to stabilizer 32 by either of valved lines35. Reilux in addition to that resulting by the use of the cold materialfrom the product sepacan be recycled to methane cracker |40 or used asfuel.

Although the simple flow diagram and arrangement of apparatus shown inFigureA l is advantageous in many respects, it is also desir-Alternatively, the gas phase able in some instances to use moreextensive processingV and equipment. This is particularly true wherelarge production is Vavailable and where the characteristics of theformation in well fluids are such that the production of the well orwells declines only very slowly, justifying a high capital investment inobtaining increased eiiiciency. Figures 2 and 3 taken togetherillustrate some of these possibilities.

Referring to Figures 2 and 3 in more detail, the production from one ormore producing wells I0, which are preferably of the distillate type,passes through valve II and line I2 into cooler I3 and pressurereduction valve I4 tov a separator absorber I5 whichl if valves I8 andI8 are closed and no absorber il is introduced by lines 20 and I1,operates as a retrograde condensation separator similar to that shown inFigure 1. One diierence, however, is that Figure 2 shows the use of anantifreeze system as one method of preventing natural gas hydratetrouble. A fluid antifreeze material, for example, calcium chloridebrine, can be circulated with the `ivell fluids through pressurereduction valve I4 and this serves to prevent the formation of naturalgas hydrates.. In the case of liquid antifreeze material, the antifreezeseparates at the bottom of the separator absorber I5 and is withdrawn byvalved line 25 under control of iioat 24 which floats at the interfacebetween the antifreeze and the hydrocarbons. The antifreeze is withdrawnto a regeneration, storage and recycling system from which it goes backinto the line either preceding or following cooler I3. In Figure 2 theregenerated antifreeze is returned by valved line 21 between the coolerI3 and pressure reduction valve I4.

It`will be understood, however, that some of these apparatusarrangements may be omitted depending upon the character of the wellfluids and the character of the subsequent operations. Thus, for exampleif the well fluids are available at moderate pressures, for instance1500 to 3000 pounds per square inch, a pressure reduction ordinarilywill not be needed and is not desirable when the distillate recovery iseiected by absorption. If the product is very low in water content or ifthe separator-absorber I5 is operated at a temperature above that atwhich hydrates form under the particular conditions involved, theantifreeze step can be omitted. An alternative method of avoiding thenatural gas hydrates is shown in Figure l, wherein the well fluids aredried by passing-them through a drier containing a solid contact masssuch as calcium chloride for example.

The well iuids enter the high pressure separator-absorber I5 and thegases, chiefly methane, are withdrawn from separator I5 by line I6. Theliquid hydrocarbons in separator I5 are withdrawn through valve 22 underthe control of float valve 2| and passed by means of line 23 to surgedrum 28. This surge drum can be operated at about the same pressure asseparator I 5 in which case it serves only as the surge drum. Or it maybe operated at a pressure intermediate that of separator I5 and that ofstabilizer 32, in which case it serves not only as a surge drum but alsoas a separator. Thus, for example, the distillate recovery vessel I5 canbe operated at 1200 pounds per square inch, the surge drum 28 at 600pounds per square inch, and stabilizer 32 at 300 pounds per square inch.Valved line 3| leading from surge drum 28 to fuel gas system 88 isprovided.

Thus whensurge drum 28 is operated as a separator, some of the gases canbe removed to fuel. The liquid present in surge drum 2l passes throughline 28 and pressure reduction valve 30' into stabilizer 32. Beforeentering the stabilizer 32 all or part of the liquid can be used to coolthe stabilized product by wholly or partially closing valve 34 andopening valves 33, thereby passing this cooled stream from the surgedrum 2l through heat exchanger 60. On the other handv it is oftendesirable to utilize the low temperature of this material from the surgedrum not al4 indirect heat-exchange material in heat exchanger 60 butrather as reiluxing material in stabilizer 32. When the stream from thesurge drum is not routed through the heat exchanger 60 prior tointroduction into the stabilizer, the

point of introduction preferably is the one corresponding to the upperof the three alternative valved lines 35.

' In stabilizer 32 hydrocarbons lighter than butane are removed and thestabilizer is pret' erably`operated at such pressure, reflux ratio, andtop temperature as to eliminate a portion of the C4 hydrocarbons notdesired in the nished motor fuel. Reflux in addition to that resultingby the use of the cold material from the surge drum 28 can, if desired,be furnished by passing the off-gases from the stabilizer 32 via line 33through partial condenser 31 to separator Il from which a part of theliquid phase can be pumped by means of pump 40 through valve 4I and line42 back into the top of stabilizer 32. I! the hot material frompolymerizer 41 is introduced into stabilizer 32 through line 53, as will-be discussed hereinafter, little or no reboiling is necessary. However,if this is not the case, i. e if a separate fractionator apparatus isused for the polymerization products, reboiling can be furnished bymeans of trapout plate 64 and heater 65. Some heating at this point maybe desirable, even if the hot polymerization products are dischargedinto the stabilizer.

Stabilized material from stabilizer 32 can be cooled by heat exchanger60 and/or cooler Il and then passed to intermediate products storagetank 63. Since the material in this intermediate porducts storage tanknormally contains a considerable amount of hydrocarbons boiling abovethe gasoline range, it can be rerun. Therefore, it is withdrawn by meansof pump 66 and passed through line 61 to rerun tower 68. When desired.the liquid product from the Fischer process may be rerun with thebottoms from stabilizer 32 which may include gasoline, polymers anddistillate hydrocarbons.

Rerun tower 68 can be operated at low pressure and is a conventionalpiece of equipment. If cooler 6I has been used, the material fromintermediate product storage tank 63 can be used to cool the hot bottomsfrom rerun tower 38 by closing valve 68 and opening valves 10, thuspassing this relatively cold stream through heat exchanger 1I. In anyevent the material to be rerun enters the rerun tower 68 by line 61. Thetower is provided with dephlegmating coil 12 and reboiling equipment 13.Stabilized gasoline of the desired endpoint is taken off through line14, passed through condenser 15 and then passed via line 16 to storagetank 11 which with proper control may contain the final gasolineproduced directly from the distillate. If the liquid product from theFischer process has not been rerun .with the intermediate product fromstabilizer 32, this gasoline can be withdrawn through valved line 18 forshipment or for further treatment. Alternatively, it mayl be withdrawnthrough valved line 18 and blended in line 8| with the gasoline producedin the polymerization operation, and this is in general desirable sinceVthe polymer gasoline has a relatively high knock rating and thedistillate gasoline has a relativelyv distillate tank 88 can be omittedand all the heavy distillate can be passed along with the heavy polymersin tank 84. 'Ihe heavy polymers separately accumulated in tank 84 is thebest absorber oil-for use in distillate separator l5. Therefore, whenthe separator i is operated as a high pressure absorber, the heavydistillate can be collected in storage tank via valved line 85- andremoved by valved line 81.

Returning now to separator 38 in connection p with stabilizer 32, theliquids from this separator alternately are passed by pump 40 throughvalve 48, line 4.4, line 45, heat exchangers 48 and line 48 into thecoils of the polymerization furnace 41.

The gases from separator 38 on the other hand can be utilized in avariety of ways which will depend for themost part upon theircomposition. Their composition in turn depends on the pressures chosenfor various parts of the apparatus and on the composition of theoriginal well fluids. If gases from the surge drum 28 are not usedasfuel, gases from separator 38 can be used as part or all of the fuel forpolymerlzer 41. Fuel gas storage tank 88 normally floats on the line. 40

gases from separator 38 do not contain large f amounts of polymerizablehydrocarbons, is to pass all or a part of these gases through valve v88,compressors 80, valve 82, compressors 83,

line 84, line |80, compressors 203, and line 204 to input well |52.polymerizer 41 discharges into stabilizer 32, to cycle the greater partof the gas from separator 38 to the'input well or wells |52. Gases fromdownstream points can be picked up and recycled ,to a point in theFischer proc'ess. For example,

valved line 201 can be provided for that purpose.

Referring now in more detail to polymerizer 41, the hydrocarbonsentering it are preheated by means of heat exchangers 48, or by one ofthem if sodesired, by control `of ow of product by valves 50, and thenpass with any desired routing through the coils of the polymerizationfurnace 41. This polymerizer is preferably operated at a temperature ofbetween about 950 and 1150 F., for instance about l025 F., and at apressure of 1000 to 3000 pounds per square inch, for example 1500 poundsper square inch.

Other types of polymerizers may be used, preferably high temperaturethermal polymerization I prefer, particularly when systems, but alsoincluding thermal and catalytic systems in which the gases are rstdehydrogenated and then polymerized in a separate operation. Such apolymerization can be applied to the synthetic crude produced by theFischer process as will be described below. Although the operation ofpolymerization involves dehydrogenation as well as polymerization. inthe strict sense of the latter term, I refer to the comblned reactions.whether occurring together or in separate steps, as polymerization. Thisis i accordance with the usage in the art.

The reaction products from the polymerizer 41 pass out through line 48and heat exchangers 48 and thence through valved lines 5|, 54, or 85. Ifdesired, the hot polymerization products from polymerizer 41 can enterseparator 55 by valved line 54 in which case valve 5I is closed. 'Iheheavy polymer may be withdrawn by valved line 58 in response to floatcontrol 51. The remaining vapors then pass by valved line 58 and one ofvalved lines 53 to stabilizer 32. This has the advantage of using asingle column for two purposes and utilizing the hot stream from thepolymerizer and the relatively cold stream from the distillate recoveryoperation to good advanltage in eliminating or cutting down the amountof reflux and reboiling necessary in connection with this tower. Whenthis operation is carried out in this fashion, tanks 83, 11 and 88 will,of course, contain `the polymer product as well as the distillateproduct, and stabilizer 81, fractionator 88, bubble tower 88 and tanks84 and 88, together with the associated equipment, can be eliminated.

On the other hand, it is sometimes advantageous to keep thepolymerization products entirely separate from those of the distillaterecovery operation, and when this is desired valves 5| and 54 can beclosed and valve 85 opened, thus sending the products from thepolymerizer 41 to a separate fractionation system. Another possibilityis to utilize a vseparate fractionation system only for such part of thepolymer products as it is desired to keep separate and to retain theadvantages lof single tower operation insofar as the bulk of the polymerproducts is concerned. This can, of course, be accomplished vby propercontrol of valves 5|, 54 and 85.

The material, if any, passing through valved line can be used, if sodesired, to heat reboiler |00, whereuponit enters fractionating column88 which is operated under such conditions that the f fractionator 88passes into stabilizer 81 through line |03 and one of the threealternative valved lines |04. The bottoms from the stabilizer iswithdrawn through valve |05 and passed through cooler |08 to, storagetank 88 as part of the stabilized polymer gasoline product. The overheadfrom stabilizer 81 passes through line |01 and partial condenser |08 toseparator |08. A portion of the liquid phase from this separator can bepassed by pump H0 through valved line III to serve as reux in stabilizer81. Likewise all or a portion can be recycled by valved line H2, line45, heat exchangers 48 and line 48 to the coils of the polymerizationfurnace 41 to produce higher ultimate yields of polymer gasoline.Alternatively, all or a portion of the liquid phase from separator |88may be routed by valved line |35 and line |1| to furnace |15 andsubsequently subjected to `catalytic polymerization together withthe-synthetic crude produced by the gascracking \and hydrocarbonsynthesis steps.

The gas phase from separator |09 may be handled in any one or more ofthe three alternative Ways discussed in connection with the gas phasefrom separator 38. Thus it may be passed through valve H3, compressors||4, valve |I5, line 45, etc. to the coils of the polymeriaer 41; orthrough valve ||6 and line ||1 to burner ||8 or fuel gas storage 88;and/or it may be passed by valved line H3, compressors H4, valve H9,compressors 93, line 94, line |90, compressors 203, and line 204 to oneor more input wells |52. This latter is ahighly desirable operation,since it is important to keep up the amount of gas available forrecycling to the formation and this gas being rich in hydrogen is aparticularly desirable material for recycling. In many instances, itwill be possible to eliminate part of the compressors referred to, sinceit will not be desired to utilize al1 of these possible alternativearrangements shown.

Reverting now to the bottoms from the fractionator 96, these can beused, if desired, to cool the bottoms from bubble tower 98 by closingvalve |20 and opening valves |2|, whereby the hot, stream passes throughheat exchanger |22 and thence through line |23 into the bubble tower 98.This bubble tower is conventionally equipped with dephlegmating means|24 and reboiling means |25; It is so operated as to eliminate a heavierthan gasoline bottoms and a gasoline overhead. The latter is passedthrough condenser |26 and line |21 to polymer product tank 99 while thebottoms pass through heat exchangers |22 and/or cooler |28 to heavypolymer tank 84.

The heavy polymer can be withdrawn from tank 84 for any desired purposethrough valved line |29 and the heavy distillate from tank 96 similarlycan be withdrawn through valved line 81. However, it is advantageous touse one or both of these materials as an absorber oil and to operatevessel I as a high pressure absorber rather than merely as a retrogradecondensation separator, since the recovery of distillate can ordinarilybe increased quite substantially by so doing.

The polymer product of gasoline boiling range can be withdrawn from tank99 through valved line |30 for storage, further treatment or use, or canbe, and preferably is, withdrawn through valve 3| for admixture with thedistillate gasoline in line 8|.

As has been pointed out above. the preferred absorber oil is the heavy'polymer separately accumulated in tank 84 and this is one of theprincipal reasons for' using a separate fractionating system on at leasta part of the polymer products. In connection with small installations,it will be apparent that this fractionating system can be simplifiedconsiderably. In the preferred operation using heavy polymers asabsorber oil, the heavy distillate is withdrawn from the system throughvalved line 81, valves 83 and |32 being closed, while such part of theheavy polymer as is by line |39. Ordinarily, the methane or gal fractionis passed concurrent to the flow through the unit as a cooling mediumaround the tubes. The methane fraction is then circulated by line |43 tothe top of the methane cracker |40 and re-enters the unit with theoxygen in line |40. These combined gases enterthe catalyst bed at about900 F. and the product gases are removed from the bottom of the methanecracker |40 at about 1600 F. Heat exchangers |4| are provided on theproduct gas line to preheat the oxygen flowing via lines |42 or |44 and|45 to the stream entering the `methane cracker. In passing through themethane cracker the methane is subjected to catalytic oxidation at atemperature of about 1600 F. and at a pressure of about i 140 pounds persquare inch. The methane fracbefore the synthesis gas reaches thesynthesis needed for absorber oil passes through valve |33,

oven |48. A portion of vthis heat is removed by heat exchanger |4| inpreheating the oxygen and the heat above about 700 F. is recovered inwaste heat boiler |41. The remainder of the heat may be discarded in awater cooler (not shown).

The oxygen for the catalytic oxidation of the methane fraction may beobtained by the electrolysis of water or by the Linde or the Linde#Frnkl process from air. In the electrolysis of water, electrode pressureof the order of 1000 atmospheres of hydrogen may be obtained for cyclingto the input well |52.

The electrolysis of the water as a source of oxygen produces a quantityof by-product hydrogen under very high pressure and this hydrogen may becycled to the underground reservoir dispensing with the recompression ofthe gases. In Figure 2 the water enters the system by line |40, theoxygen being led to line |42 by valved line 49;` the hydrogen passingvia. valved line |50and line |5| to input well |52. When the oxygennecessary for the gas-cracking step is produced by the Linde orLinde-Frnki process, there results a volume of by-product nitrogen whichis available at an elevated pressure. The air is passed through heatexchanger |31 and the recovered oxygen is led to line |42 by valved line|53, the recovered high pressure by-product nitrogen passing via line|54 to line |5| and ultimately to input well |52. Thus by my'processthere is no deficiency of recycled gas and an increased quantity ofmotor fuel is produced from the well fluids.

According to the preferred procedure, the methane fraction which mayincludeselected higher hydrocarbons is subjected to catalytic oxidationat high temperature and under moderate pressure according to the knownprocess. Suitable temperatures are of the range of 1450 F. to

1700 F. andpressures may range from atmospheric up to about pounds persquare inch.

A suitable catalyst for use in the synthesis oven are metals of theeighth group, i. e. iron, cobalt and nickel, with cobalt beingparticularly useful. The catalyst may be supported on kieselguhr, forexample, and is rendered more active by the presence of small amounts ofdiftlcultly pressing the discard gases cycled to the input well.

Alternatively, the synthesis gas may be produced by reacting the methanewith steam. This latter reaction is less desirable since it is notexothermic, as is the reaction between methane and oxygen, and furthersince it produces an excess of hydrogen, the mol ratio of hydrogen t0carbon monoxide being about 3:1. This can be compensated by includingsome hydrocarbons higher than methane with the methane fraction or byintroducing carbon monoxide from another source. 'I'he gaseous reactionproducts of the catalytic oxidation are, of course, carbon monoxide andhydrogen. From this carbon monoxide and hydrogen, hydrocarbons aresynthesized by the Fischer process, A mol ratio of hydrogen to carbonmonoxide of about 2:1 ordinarily is used to produce hydrocarbonspredominating in `paralllns. Decreasing the hydrogen content of thesynthesis gas gives a more olenic product. Thus a hydrogen to carbonmonoxide ratio of about 1.5 to 1 yields more olens.

The synthesis gas comprising largely hydrogen and carbon monoxide iswithdrawn from methane cracker |40 Aby line |55 by which it passes tothe synthesis oven |46. In oven |46 the carbon monoxide and hydrogen arereacted with each other and with any hydrocarbons present to producehigher molecular weight hydrocarbons largely of the gasoline boilingrange. This step is well known in the art and it is contemplated that itmay be carried out under any one of the variety of conditions underwhich it is known to operate. Thus it may be carried out at pressuresranging from atmospheric up to about 150 pounds per square inch, orsomewhat higher,

and within the temperature range of between about 300 F. and 400 F., forexample 383 F., although somewhat higher and somewhat lower temperaturesmay be used if desired.

It is well recognized that the Fischer synthesis is highly exothermicand if uncontrolled the heat effect raises the temperature of thereaction to a point where methane and carbon are produced. At the sametime it is necessary to keep the reaction temperature between narrow.limits. The dissipation of the heat of reaction may be effected bycirculation of water around the catalyst containers, thereby generatingsteam suitable for process use.

The synthesis product is removed from the oven |46 by line |56 toseparator |51. If desired, waste heat boiler |58 may be on line |56 tocool the reaction product prior to introduction to the separator |51.

Considerable quantities of water are produced in the Fischer process andthis water ordinarily is removed from the hydrocarbons and dis- The'heavy liquid fraction from a Fischer synthesis frequently has a verylow octane number and therefore'it may be desirable to send the productto a reforming step by valved line |64. However, where a nished motorfuel is produced in the Fischer synthesis `it may be pumped by pump |66,line |65 and line 61 to rerun tower 68.

The gaseous product of the synthesis is taken oil! overhead fromseparator |51 by line |61, compressed by compressors |68, and sent tocooler |69 before entering separator |10. The liquid fraction fromseparator |10 is withdrawn by line |1| and passed in heat-exchangerelationship with the synthesis products going to the product separator|51. Heat exchanger |12 is provided for this purpose. The liquidfractions comprising substantial amounts of olens are sent via 'line |1|and pump |14 to furnace |15. 'I'he gaseous products from separator |10are withcarded from the system through valved line 202 l drawn by line|16 and passed to absorber |11, wherein it is subjected to the action ofa circulating absorber oil. The rich absorber oil is withdrawn fromabsorber |11 by line |18, passed through heat exchanger |19 andintroduced to fractionator |80. Fractionator is provided with aconventional dephlegmating means |8| and reboiler |82. 'I'he bottomsfrom fractionator |80 is passed via line |83 and pump |84 through coolerand introduced as the lean absorber oil in absorber 11 via line |86. Thetail gases from absorber |11 comprising predominantly hydrogen arewithdrawn by line |81. 'Ihese gases may be recycled to the methanecracker |40 by valved line |89. 'I'hey may be compressed by compressors|88 and recycled to the input well by line |90, or the tail-gases may besent to fuel by valved line |9|.

Reverting to fractionator 80, the gaseous fraction is withdrawn overheadby line |92, compressed by compressors |93, and passed to furnace |15.'I'hus the bottoms from separator |10 and the overhead from fractionator|80 are heated in the same furnace. The hot feed passes by line |94 tocatalyst chambers |95 and |96, where polymers are formed. l

The elevated temperature maintained in the polymerization zone isordinarily in the range of 300 to 500 F. and the pressure usually isabout 150 to 1500 pounds per square inch. The above conditions are forcatalysts of the phosphoric acid-kieselguhr or metal pyrophosphatetypes. Sulfuric acid and aluminum halide may be used at lowertemperatures. Valves |91 and |99 are provided whereby one catalystchamber is onstream, while the other is being regenerated.

The reaction products' are removed from the catalyst chamber by line|99, and can be. passed by valved line 200 and valved line 95 tofractionator 96. Alternatively, the reaction products may be introducedby valved line 20| to valved lines 5| or 54 and blended with thereaction products from polymerizer 41.

Vessel I5 when operated as an absorber can usually be operated at asomewhat higher pressure and, if desired, at a slightly highertemperature than when operated as a retrograde condensation separator.More specifically as an absorber its pressure may range from 1000 to4000 pounds per square inch, usually from 1200 to 3000 pounds per squareinch, for instance 2000 pounds per square inch. The absorber oil in anydesired ratio, for example two to six gallons per thousand cubic feet ofgas, can be introduced above bailles |34or part of it or even all of itcan be passed through cooler Il into the absorber along with the wellfluids. 'The absorber oil, of course, is 'removed from vessel i5 alongwith the distillate hydrocarbons and finds its wayV through surge drum28 and stabilizerV the'unewly produced heavy polymer is continu-v ouslysent to the absorber as an absorption medium, since its aromaticcharacter and its high critical temperature make it possible to operatelseparator-absorber l5 at a higher pressure than would otherwise be thecase. If desired, the material to be used as absorber oil may befractionated.. Thus for'instance the heavy polymers in tank lcould befractionated and the desired fraction could be sent to the absorber I6.For economic reasons the operation at a higher pressure is moredesirable. i

It is to be understood, of course, -that the var-- ious ilow diagramspresentedv are merely illustrative of some oi' the possibilities andother alternative routings will occur to those skilled in the art inview of this description.- Therefore my invention is not restricted tothe details shown. Likewise, it will be understood that these flowdiagrams are simplified for purposes of convenience and that variousitems of pumping and compressing equipment,A insulation control devices,safety equipment, and various other 'details are not indicated.

Having described my invention what I claim is:

l. A method of effecting maximum recovery from a high pressure petroleumreservoir and of preparing liquid hydrocarbons from high pressure wellfluids recovered therefrom comprising the steps of simultaneouslygenerating oxygen and a by-product gas of the oxygen generation at aboutthe pressure of the high pressure reservoir, injecting said highpressure by-product gas into a high pressure petroleum reservoir toeiect maximum recovery of high pressure well fluids, separating saidwell fluids at a high pressure into at least one fraction rich innormally gaseous hydrocarbons and at least one fraction rich indistillate motor fuel hydrocarbons, generating a synthesis gascomprising carbon monoxide and hydrogen by treating said normallygaseous hydrocarbons at an elevated temperature in the presence of saidgenerated oxygen, subjecting the said synthesis gas to an'exothermichydrocarbon synthesis step, fractionating the product from saidhydrocarbon synthesis into at least one gas fraction and at assura fleast one liquid fraction, said liquid fraction being rich in motor fuelhydrocarbons.

2. A method of effecting maximum recovery y from a high pressurepetroleum reservoir and of preparing liquid hydrocarbons from highpressure well fluids recovered therefrom comprising the steps ofsimultaneously generating oxygen and a by-product gas of the oxygengeneration at about the pressure of the high pressure reservoir, in-Jecting said high pressure by-product g in to a high pressure petroleumreservoir to eifect maximum recovery of high pressure well fluids,separating said well fluids at a high pressure into at least onefraction rich in normally gaseous hydrocarbons and at least one fractionrich in distillate motor fuell hydrocarbons, cycling at least a portionofthe high pressure normally gaseous hydrocarbons along with the highpressure byproduct gas to the high pressure petroleum reservoir toenhance the retrograde vaporization effeet of the pressuring gases,generating a synthesis gas comprising carbon monoxide and hydrogen bytreating said normally gaseous hydrocarbons at an elevated temperaturein the presence of said generated oxygen, subjecting the said synthesisgas to an exothermic hydrocarbon synthesis step, fractionating theproduct from said hydrocarbon synthesis into at least one gas fractionand a .least one liquid fraction, said liquid fraction be ng rich inmotor fuel hydrocarbons.

3. A me' od of eil'ecting maximum recovery from a highpressure petroleumreservoir and of preparing liquid hydrocarbons from high pressure wellfluids recovered therefrom the steps comprising simultaneouslygenerating oxygen and a by-product gas of thev oxygen generation at ahigh pressure of the magnitude of the pressure existing in a petroleumreservoir, injecting said high pressure by-product gas into the highpressure petroleum reservoir to effect maximum recovery of high pressurewell fluids, separating said well fluids at high pressure into at leastone fraction rich-in methane and at least one fraction rich indistillate motor fuel hydrocarbons, generating a synthesis gascomprising carbon monoxide and hydrogen by cracking said fraction richin methane in the presence of said oxygen, subjeeting said synthesis gasto an exothermic hydrocarbon synthesis step, recovering from the productof said hydrocarbon synthesis .step at least one synthesis fraction richin motor fuel hydrocarbons, and blending said distillate motor fuelhydrocarbons and said synthesis fraction.

GEORGE L. PARIU-IURST.

